Motor Overload CTÆS

[Ahr35181]

I’ve come across two similar 60/1A ct’s, one is marked two primary turns, the other three primary turns. Does this mean two / three primary turns respectively are required to give a 60/1 ratio in each case? To me, a 60/1A ct is 60/1 with one primary passing through???

Thanks in advance.

Alan

 

[busbar]

If manufacturer’s literature is not available, a ratio check may be in order. Excite the secondary at ~6 volts at line frequency and measure primary-side voltage with 1-3 turns through the primary window.

 

[aolalde]

The ratio of both is 60/1. The turns are different.

The one with two primary turns must have 120 T in the secondary. The 3T must have 180 turns in the secondary. See the rated current capacity or Burden for each. Are them from the same manufacturer?

Be careful since open secondary of CT's could induce very high voltage. Better keep the secondary short circuited and test with a clamp on ammeter if current is circulated in the primary.

If test with voltage apply 120 VAC to the secondary (120 or 180 turns side) and measure the small induced voltage in the primary, less than 2 volts ( 2 or 3 turns), Get the CT ratio by the measured inverse volts ratio.